The long-term goal of this laboratory is to understand the contributions made by the primate's cerebral cortex to voluntary motor behavior. Experiments will focus upon the frontal eye field in the rhesus monkey's cerebral cortex and its role in the control of eye movements. Frontal eye field removal is detrimental to the initiation and performance of saccades in complex visuomotor tasks. In addition, frontal eye field neurons exhibit several types of visuomotor activity, identified by recording from behaving animals, including: visual activity; movement related activity preceding saccades; postsaccaddic activity; and activity related to fixation and foveal visual stimuli. This proposal will refine our ideas about how and to what extent the frontal eye field participates in eye movement control, emphasizing the contributions it makes to the complex network of brain regions within the oculomotor system. Four experimental approaches will be used: 1) Characterize the message sent by the frontal eye field to its cortical and subcortical targets by identifying the efferent target of single neurons with antidromic excitation, and then classifying the activity of those neurons during visuomotor behavior. Of particular interest are the types of messages sent by the frontal eye field to its termination sites in the brainstem reticular formation, the supplementary cortical eye field, and the contralateral frontal eye field. 2) Determine the regional and laminar distribution of neurons belonging to the major activity classes by making comprehensive series of electrolytic marking lesions at the recording sites of identified neurons. 3) Examine the relationship between the firing pattern of frontal eye field neurons with movement activity, and the dynamics of the eye movement that their firing precedes. For example, to answer the question: Are changes in presaccadic firing rate accompanied by changes in saccade trajectory or peak velocity? 4) Follow up on evidence from ablation studies that the frontal eye field participates in smooth pursuit. Techniques will be used that distinguish sensory from motor signals related to the pursuit of moving visual targets. The brains of rhesus monkeys and humans are similar, and the principles of function and organization revealed by these experiments may also apply to humans.